Such a self-locking T-piece is known, for example, from US 2002/0162554 A1. The prior-art self-locking T-piece has a line section, at both ends of which flexible tubes of the breathing gas line can be connected. The connection line, which opens into the line section, is approximately at right angles to the line section. A valve body has a valve disk with an external diameter that is larger than the diameter of a valve seat at the end of the connection line. The valve seat may be formed by a continuation of the connection line into the interior of the line section; the valve disk has a larger external diameter in this case than the internal diameter of the connection line, so that it can cover the opening of the continuation of the connection line, which opening opens into the line section, in order to thus block the connection line. The valve body has, furthermore, a shaft, which carries the valve disk. A spring, which applies a force directed towards the connection line to the valve body, acts on the valve body, so that the valve disk is pulled onto the mouth opening of the connection line for sealing. The shaft of the valve body is connected to an end piece, which can slide in the connection line. This end piece forms an abutment for the spring and has the further task of lifting the valve body out of the sealing position thereof when an attachment is attached to the connection line, where said attachment has a line, which is inserted into the outer end of the connection line. When the line of the attachment is being pushed into the connection line, the attachment comes into contact with the end piece of the valve body and thus lifts the valve body out of the sealing position thereof at the mouth of the connection line. Conversely, the valve closes again when the attachment is again removed from the connection line by being pulled off.
Such self-locking T-pieces are used in mechanical respiration. Typical attachments, which are connected to a breathing gas line, are, for example, water traps, nebulizers and sensors. The valve is automatically opened during the mounting of the attachment and it closes again during the removal of the attachment. Such T-pieces are increasingly frequently used only for single-time use and are used at only one patient for the short-term use and are then disposed of. It is especially important in the case of such T-pieces for single-time use to build them with the smallest number of parts possible and to make the mounting operations during the assembly of the self-locking T-piece as simple as possible.
Another self-locking T-piece is known from U.S. Pat. No. 4,951,661 A. The self-locking T-piece has a valve body with U-shaped cross section, which carries a flexible valve membrane on its top side. A spring element presses the membrane and thus the U-shaped valve body from the tip, so that the valve membrane closes the opening of the connection line. When a device to be connected is inserted into the connection line, the U-shaped valve body is lifted thereby, as a result of which the valve membrane is likewise lifted out of the valve seat.